It's probably just tire noise. Does it get louder as you get faster? Does the hum sound anything like how a lifted truck or a semi sounds like?
I have a pickup and it's not that sound. I have the same tires on my GT but they are not staggered and do not make that noise. The Pirellis cost a lot less than the Nittos or Mickeys. My GT has 20K on them and they still have a lot of tread. The hum does not sound like tire whine, it's a lower tone but yes it increases with speed. I'll just learn to live with it.
1989 Blue LX Hatchback
2001 Red SVT Cobra Convertible (Phoenix)
2002 Black/Red GT (Ginger)
2011 Red Candy Metallic V6 (Manfred)
2016 Magnetic Metallic GT (Susie II)